An Australian held in a Danish prison for three weeks for organising a protest during the Copenhagen climate change conference has been released.

Natasha Verco was arrested on December 15, a day before the biggest protest march during the United Nations talks in Copenhagen.

The chief prosecutor for the Copenhagen police, Dorit Borgaard, says Verco was released overnight along with American citizen Noah Weiss.

Their case has been adjourned until March 16 when they will face charges of attempted assault of a police officer and planning to disturb public order.

If convicted, they face up to six months in jail.

Verco insists she organised a peaceful event during the conference and denies accusations that she assaulted a police officer and planned to disturb public order.

"I participated in organising people to speak about climate change with youth delegates for the UN," she said.

"They say I organised riots and when we said that riots didn't happen, they said, 'No, you were charged with organising riots that were stopped by the good work of the police'.

"So they're charging me with organising things that never happened.

"I think it's a huge departure from what I understand to be any form of legal process, a huge departure from any form of justice."

Verco says she was not doing anything illegal.

"I wasn't at a protest. I wasn't on my way to a protest. I was riding along the side of the road.

"When I asked them what was going on (and) were they just picking up anybody who was wearing black clothes - I had a black jacket on and some black pants - they said, 'no we've been hunting you'."

Verco says she was scared because the police did not say why she was being arrested.

"I asked them what they were picking me up for and they said,'we don't need to tell you anything'.

"I kept enquiring because I was quite scared at this point, and they pushed me down onto the floor of the van, they folded my legs up and they sat on my legs and they put their feet on my back."

Verco says officials closed the court for her arraignment and that the evidence presented was "ridiculous".

"They had recordings of conversations of mine on my telephone for the last three months and they had evidence from somebody else's case about a protest they were involved in," she said.

"On the basis of both of those things they said they had sufficient grounds to hold me, but the conversations that they recorded, in one of them I was trying to help organise accommodation for some Italians.

"In another one I was talking about trying to get funding for people to come. In another one I was organising a meeting.

"I really am gobsmacked. I can't really understand how they managed to lock me up for three-and-a-half weeks on that basis."